Pressure regulators that reduce or cut off inlet flow of a fluid when the outlet pressure starts to exceed a predetermined maximum and that open or increase flow when the outlet pressure has been sufficiently reduced are well known in the art. Such regulators generally include a coil spring that biases a valve member open, and a pressure-sensing element responsive to excess inlet pressure which closes the valve member. In this arrangement, increasing liquid pressure compresses the spring to force the valve member towards a valve seat. As the valve member approaches the valve seat, liquid flow through the regulator becomes more restricted. When the defined pressure level is reached, further flow restriction is stopped, or the valve member contacts the valve seat to cut off flow. When the output pressure drops below the defined pressure, the valve member moves away from the valve seat and flow increases. This cycle is rapidly repeated over and over to maintain the output pressure at the desired setting.
Numerous pressure regulating devices teach the use of a coil spring, such as U.S. Pat. No. 3,412,650 by Stang, U.S. Pat. No. 3,547,427 by Kelly, U.S. Pat. No. 3,603,214 by Murrell, U.S. Pat. No. 3,747,629 by Bauman, U.S. Pat. No. 3,825,029 by Genbauffe, U.S. Pat. 4,074,694 by Lee, U.S. Pat. No. 4,621,658 by Buezis et al., U.S. Pat. No. 4,744,387 by Otteman, U.S. Pat. No. 5,141,022 by Black, and U.S. Pat. No. 5,732,736 by Ollivier. However, a need exists for a pressure regulator device without a spring coil, thereby resulting in a more reliable device with fewer parts which is easier to assemble and costs less.
The majority of the subject pressure regulators of the above-referenced patents are manufactured to provide a single, specific fluid outlet pressure or be adjustable between a high and a low setting. However, there also exists a need for a variable pressure regulator device that allows for the selection, from a range of values, of a desired fluid outlet pressure by a user. This capability is particularly desirable in connection with small pumps used in the medical field wherein fluids are being dispensed to a patient.